The present invention is related to a technique for drawing on an optical disk.
Among optical disks such as CD-R (Compact Disk-Recordable), CD-RW (Compact Disk-Rewritable), and DVD-R (Digital Versatile Disk-Recordable), since contents of recorded data cannot be discriminated from each other by human eyes, it is practically difficult to discriminate the respective optical disks from each other based upon outer appearances of these optical disks. As a consequence, the following technical ideas are proposed: That is, characters, symbols, or figures/pictures are drawn on optical disks, thereby these optical disks can be simply discriminated from each other based upon the outer appearances thereof. For instance, JP-A-2004-5846 discloses such a technical idea that an optical disk drawing apparatus irradiates laser light according to image data onto a discoloring layer formed on an optical disk so as to discolor the laser irradiated region thereof, thereby an image is formed.
On the other hand, in order to freely edit images to be drawn on optical disks by users, it is convenient to employ a host apparatus such as a personal computer which is connected to an optical disk drawing apparatus. The host apparatus can have a superior operability, and are executable of high-performance drawing application programs. In this case, when image data produced by employing the drawing application program are supplied from the host apparatus to the optical disk drawing apparatus, the supplied image data are stored in buffer memory by the optical disk drawing apparatus. Then, image data which is properly read out from the buffer memory is encoded, and the encoded image data is supplied to a laser driver so as to irradiate the laser light onto the optical disk.
When a data amount of image data supplied from the host apparatus to the optical disk drawing apparatus is increased, a communication load between the host apparatus and the optical disk drawing apparatus is increased. As a result, in view of suppression of the communication load, it is desirable to reduce the data amount of the image data supplied from the host apparatus to the optical disk drawing apparatus as small as possible.
Also, there is a case that a pace for supplying image data from the host apparatuses to the optical disk drawing apparatuses cannot follow up reading speeds of the image data by the optical disk drawing apparatus. In this case, there is no image data which should be read out from the buffer memory in the optical disk drawing apparatus. As a result, a so-called “buffer under run error” may occur, so that the optical disk drawing apparatus must interrupt the drawing process operation.